Already created an SR for this, but thought I'd try my luck here as well.

DataSynchronizer Build 428
Groupwise 8 HP 2
All new Windows Mobile 6.x devices

We still have Groupwise Mobile Server users, so after updating the DataSynchronizer to build 428 I wanted to switch some users to the DataSynchronizer. No luck. The device is added to the user in the DataSynchronizer and the security policy is enabled on the device (4 number PIN), but the Windows Mobile 6.x won't sync and ActiveSync throws an 0x80004005 supportcode at me. Existing Windows Mobile devices who were present in the DataSynchronizer before the update still work as far as I can tell. No angry users just yet

I can still add Android devices to new users without any problems.